Change the parent-child relation in a treeview control at runtime

[mpv55]

I want to program a water supply pipeline network in a treeview control. It has five node (junctions). The parent-child relation is based on a parameter (say pressure).

Initially, the node 1 is parent and its child nodes are 2 and 3. The node 3 has child nodes 4 and 5.

At run time the pressure changes. Now, node 3 is parent and its child nodes are 1, 4 and 5. The node 1 has child node 2.

It could be easier to show in a figure, but I donot know the procedure to attach or insert a figure. sorry.

Please advise me to handle such changes in the paren-child nodes relation in the treeview control.

Thanks

[jmcilhinney]

Each TreeNode has a Nodes property which is a collection containing its child nodes. They are just collections like any other, so you can Add and Remove items like you can any other collection. The TreeView also has a Nodes collection, which contains the top-level nodes.

[4x2y]

You must give each node a unique name (key) e.g. "Node1","Node2", etc..., to move node from one place to another, use code like this

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim n1 As TreeNode
        Dim n3 As TreeNode
        n1 = GetNodeByKey("Node1")
        n3 = GetNodeByKey("Node3")
        n1.Remove()
        n3.Nodes.Add(n1)
    End Sub
 
    Private Function GetNodeByKey(ByVal strKey As String) As TreeNode
 
        Dim aFindResult As TreeNode() = TreeView1.Nodes.Find(strKey, True)
        Dim tvnRet As TreeNode = Nothing
 
        For j As Integer = 0 To aFindResult.Length - 1
            If aFindResult(j).Name = strKey Then
                tvnRet = aFindResult(j)
                Exit For
            End If
        Next
 
        Return tvnRet
 
    End Function

You must take care to not move node to one of its children

[mpv55]

Thanks for your help. Actually, I could not explained it properly in the text. It could be easy with a figure to explain. Now, I tried to create the node structure for three cases.

1. Initially, the pressure at node 0 is high and the node structure is as programmed in InitialTree.

2. the pressure at node 1 is high and the node structure is as programmed in InitialTree1. It is obtained on clicking button1.

3. the pressure at node 2 is high and the node structure is as programmed in InitialTree2. It is obtained on clicking button2.

It can be observed that the initial connection structure of nodes is mentained. I want to do it in the program depending on the pressure of any node in the original treeview control.

Any help is appreciated.
Thanks

Public Class Form1
    Dim tNode(6) As TreeNode
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Call initialTree1(TreeView1)
 
    End Sub
  
 
    Private Sub initialTree(ByVal tv As TreeView)
        tv.Nodes.Clear()
        Call totalNodes()
        tv.Nodes.Add(tNode(0))
        tv.Nodes(0).Nodes.Add(tNode(1))
        tv.Nodes(0).Nodes.Add(tNode(2))
        tv.Nodes(0).Nodes.Add(tNode(3))
        tv.Nodes(0).Nodes(1).Nodes.Add(tNode(4))
        tv.Nodes(0).Nodes(1).Nodes.Add(tNode(5))
        tv.Nodes(0).Nodes(0).Nodes.Add(tNode(6))
    End Sub
 
 
    Private Sub initialTree1(ByVal tv As TreeView)
        tv.Nodes.Clear()
        Call totalNodes()
        tv.Nodes.Add(tNode(1))
        tv.Nodes(0).Nodes.Add(tNode(0))
        tv.Nodes(0).Nodes.Add(tNode(6))
        tv.Nodes(0).Nodes(0).Nodes.Add(tNode(3))
        tv.Nodes(0).Nodes(0).Nodes.Add(tNode(2))
        tv.Nodes(0).Nodes(0).Nodes(1).Nodes.Add(tNode(4))
        tv.Nodes(0).Nodes(0).Nodes(1).Nodes.Add(tNode(5))
    End Sub
    Private Sub initialTree2(ByVal tv As TreeView)
        tv.Nodes.Clear()
        Call totalNodes()
        tv.Nodes.Add(tNode(2))
        tv.Nodes(0).Nodes.Add(tNode(0))
        tv.Nodes(0).Nodes.Add(tNode(4))
        tv.Nodes(0).Nodes.Add(tNode(5))
 
        tv.Nodes(0).Nodes(0).Nodes.Add(tNode(1))
        tv.Nodes(0).Nodes(0).Nodes.Add(tNode(3))
        tv.Nodes(0).Nodes(0).Nodes(0).Nodes.Add(tNode(6))
    End Sub
 
 
    Private Sub totalNodes()
        Dim i As Integer
 
        For i = 0 To 6
            tNode(i) = New TreeNode
            tNode(i).Name = "Node" + i.ToString
            tNode(i).Text = "Node" + i.ToString
        Next
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        
        Call initialTree(TreeView1)
 
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Call initialTree2(TreeView1)
    End Sub
End Class

[jmcilhinney]

As I have already said, to move a node you simply Remove it from the Nodes collection of its current parent and Add it to the Nodes collection of its new parent.

[4x2y]

Are you going to work with these nodes only?

If Node3, 4, 5 or 6 gets high pressure, how the structure will look?

[mpv55]

Thanks. It is just an example. there may be more nodes and any node can have high pressure. But the initial structure of nodes will remian same.
I do appreciate your help.

[4x2y]

Sorry for delay!

Try this code

Add two TreeView controls, TreeView1 which will be the original structure, TreeView2 which will show the new structure.

Public Class Form1
    Dim tNode(6) As TreeNode
 
 
    Private Sub initialTree(ByVal tv As TreeView)
        tv.Nodes.Clear()
        Call totalNodes()
        tv.Nodes.Add(tNode(0))
        tv.Nodes(0).Nodes.Add(tNode(1))
        tv.Nodes(0).Nodes.Add(tNode(2))
        tv.Nodes(0).Nodes.Add(tNode(3))
        tv.Nodes(0).Nodes(1).Nodes.Add(tNode(4))
        tv.Nodes(0).Nodes(1).Nodes.Add(tNode(5))
        tv.Nodes(0).Nodes(0).Nodes.Add(tNode(6))
    End Sub
 
    Private Sub totalNodes()
        Dim i As Integer
 
        For i = 0 To 6
            tNode(i) = New TreeNode
            tNode(i).Name = "Node" + i.ToString
            tNode(i).Text = "Node" + i.ToString
        Next
    End Sub
 
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Call initialTree(TreeView1)
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ' State 1
        SetHighPressureNode(TreeView1, TreeView2, GetNodeByKey("Node1", TreeView1), GetNodeByKey("Node0", TreeView1))
 
        'State 2
        'SetHighPressureNode(TreeView1, TreeView2, GetNodeByKey("Node2", TreeView1), GetNodeByKey("Node0", TreeView1))
    End Sub
 
    Private Sub SetHighPressureNode(ByVal tvOriginalTree As TreeView, ByVal tvWorkingTree As TreeView, ByVal tvnHighPressureNode As TreeNode, ByVal tvnLowPressureNode As TreeNode)
        Dim tvnHighClone As TreeNode
        Dim tvnLowClone As TreeNode
        Dim tvnNewHigh As TreeNode
        Dim strOldName As String
 
        tvWorkingTree.Nodes.Clear() ' Clear working tree nodes
 
        tvnHighClone = tvnHighPressureNode.Clone ' Copy high pressure node
        tvnLowClone = tvnLowPressureNode.Clone ' Copy low pressure node
 
        tvWorkingTree.Nodes.Add(tvnHighClone) ' Add copied high pressure node to the working tree root
        tvnNewHigh = GetNodeByKey(tvnHighClone.Name, tvWorkingTree)
        strOldName = tvnHighClone.Name ' Store name
        tvnNewHigh.Name = "blabla-blabla" ' Chenge name in order to not find it
        tvnNewHigh.Nodes.Insert(0, tvnLowClone)
 
        GetNodeByKey(strOldName, tvWorkingTree).Remove() ' Remove tvnHighPressureNode from its original place.
        tvnNewHigh.Name = strOldName 'Restore original name.
 
    End Sub
 
    Private Function GetNodeByKey(ByVal strKey As String, ByVal tvTree As TreeView) As TreeNode
 
        Dim aFindResult As TreeNode() = tvTree.Nodes.Find(strKey, True)
        Dim tvnRet As TreeNode = Nothing
 
        For j As Integer = 0 To aFindResult.Length - 1
            If aFindResult(j).Name = strKey Then
                tvnRet = aFindResult(j)
                Exit For
            End If
        Next
 
        Return tvnRet
 
    End Function
End Class

It works fine for the nodes example you provide, i hope it works fine for any nodes count and any nodes structure.